A white organic light emitting device is capable of generating efficient and saturated white light and has features such as a low driven voltage, good flexibility of material, and a large area for display. Therefore, the white organic light emitting device has a great application potential in fields such as information display and solid state lighting. However, factors such as high production cost and unstable performance restrict industrialization process of the white organic light emitting device. From a view of device structure, the white organic light emitting device is mainly classified as a single-layer light emitting structure and a multilayer light emitting structure. A disadvantage of a device with the single-layer light emitting structure is low light emitting efficiency. A device with the multilayer light emitting structure is used to generate white light by complementary color layers (such as a blue light layer and a yellow-orange light layer), or implement white light emission by multiple light emitting layers of three primary colors of red, green and blue. The multilayer light emitting structure has a better performance and ideal white light can be obtained by controlling each light emitting layer, but the light emitting layers may have different light emitting efficiency due to different driven voltages and may have different operating lives, which may affect chromaticity coordinates and stability.
The ideal white light is implemented by mixing the three primary colors of red, green and blue, and a waveband of the emitted light of materials should cover the whole visible light region, so that full spectrum emission can be acquired, and light emitted by a prepared device has a saturated color and a high color rendition index (CRI).
Performance of the organic light emitting device is related to the material and may also be adjusted by changing the structure of the light emitting diode. A Fabry-Perot (F-P) optical microcavity effect of the organic light emitting device causes an increase of intensity of an emission peak at a certain wavelength and a narrowed band, and tunability of the wavelength and color display can be achieved. The organic light emitting diode having the microcavity effect has a structure capable of selecting an optical mode by a microcavity, therefore narrowband emission of a particular wavelength can be achieved.
The organic light emitting diode is formed by an anode, a cathode and an organic layer which includes a light emitting layer. To improve transportation and balance of electrons or holes, the organic light emitting diode usually includes an electronic (hole) transport layer and an electron (hole) injection layer. In preparing the light emitting diode with the microcavity structure, a reasonable design for an optical length of the cavity is required, and a resonant cavity with reflectors in which light is reflected back and forth is also required, where one of the reflectors is usually formed by a metal electrode of the organic light emitting diode.